1. Field of the Invention
This invention relates to vehicle hazard warning lights and, more particularly, to the enhancement of such lights to give more effective warnings that a disabled or stalled vehicle is a hazard to other vehicles approaching from the rear.
2. Description of the Prior Art
Passenger vehicles and light trucks are the largest majority of motor vehicles in the United States. Since 1986 all new passenger vehicles, and since 1994 all new light trucks, have been required to include, as standard equipment, a center high mounted rear stop light (“CHMSL”) by Federal Motor Vehicle Safety Standard 108, and corresponding regulations and laws of the National Highway Traffic Safety Administration (“NHTSA”) and the several states.
This requirement originated from tests performed in 1983 by NHTSA which showed that CHMSLs in taxi cabs and corporate fleets appeared to reduce rear impact crashes by about 35%. However, as time went on, these successful results declined until in 1989, NHTSA found that CHMSLS, in the long term, would only prevent rear impacts in passenger cars by about 4.3%, and by an estimated 5.0% in light trucks. Apparently, as drivers became more accustomed to the CHMSLs, the efficacy of such devices wore off (NIHTSA Technical Report Number DOT HS 808 696, “The Long-Term Effectiveness of Center High Mounted Stop Lamps in Passenger Cars and Light Trucks”, March 1998). The purpose of CHMSLs is to avoid collision of a car or light truck in the rear by another approaching vehicle, by signaling that the lead vehicle is braking or has stopped.
A serious hazard arises when a vehicle malfunctions so badly as to become no longer drivable and thus vulnerable on or beside a busy road or highway. To warn of this hazard, all U.S. vehicles are required to have a 4-way flasher system that can be driver initiated to simultaneously flash the two front and two rear turn signal lamps. State vehicle codes require such flashing lamps to be used by the operator of a vehicle that is stopped or disabled (e.g., Pennsylvania Vehicle Code Title 75, § 4305). Some regulations also permit such flashing lamps to be used by drivers while approaching, overtaking or passing an accident or hazard to warn other oncoming drivers of such emergencies (e.g., California Vehicle Code, § 25251 (a)(5).
Despite the advent and long term use of 4-way flashing signal lamps and CHMSLs, rear impact vehicle accidents, especially collisions with stopped or disabled vehicles, continue to be a serious problem in the United States.